The different parts played by hydrodynamic modelling in performance assessment of low level radwaste repository

According to the relevant Fundamental Safety Rule, the ''Centre de Stockage de l'Aube'' (CSA) has been built on a simple aquifer system perfectly isolated from underlying aquifers and with well defined outflow locations. In addition, each repository cell must be out of reach of the highest free surface water level. The site hydrogeological study has been conducted through a very large site characterization work. Early hydrogeological site modelling and characterization work made it possible to gather hydrogeological field data into a coherent conceptual model expressed through a simple computer tool. This first stage made up of qualification and development phases was followed by applications on the aquifer behaviour and on the highest water level evaluation. Hydrogeological modelling has played a key role in the French disposal concept from site selection to the final performance assessment. (author). 6 refs., 8 figs